Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
Xiao Deming
  2. Issuer Name and Ticker or Trading Symbol
MONOLITHIC POWER SYSTEMS INC [MPWR]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
Pres. of MPS Asia Operations
(Last)
(First)
(Middle)
79 GREAT OAKS BLVD
3. Date of Earliest Transaction (Month/Day/Year)
02/06/2017
(Street)

SAN JOSE, CA 95119
4. If Amendment, Date Original Filed(Month/Day/Year)
6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)
2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)
4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)
5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)
6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)
7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Common Stock 02/06/2017   S(1)   5,517 D $ 88.2535 266,873 D  
Common Stock 02/07/2017   A   68,604 (2) A $ 0 335,477 D  
Common Stock 02/07/2017(3)   M(3)   4,876 (3) A $ 0 340,353 D  
Common Stock               2,197 I by Spouse

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)
2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)
5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)
6. Date Exercisable and Expiration Date
(Month/Day/Year)
7. Title and Amount of Underlying Securities
(Instr. 3 and 4)
8. Price of Derivative Security
(Instr. 5)
9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)
10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)
11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Performance Shares (3) 02/07/2017(3)   M(3)     4,876 (3)   (3)   (3) Common Stock 4,876 $ 0 56,174 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
Xiao Deming
79 GREAT OAKS BLVD
SAN JOSE, CA 95119
      Pres. of MPS Asia Operations  

Signatures

 By: Saria Tseng For: Deming Xiao   02/08/2017
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) The reported sales were to cover taxes upon the vesting of restricted stock units, as required by the Company's equity incentive plans.
(2) On February 3, 2015, the reporting person was granted a target of 24,213 shares of restricted stock units subject to satisfaction of pre-determined, performance-based vesting criteria. On February 7, 2017, the Company's Board of Directors determined that those performance criteria for the restricted stock units had been satisfied, which resulted in 44,391 additional shares being achieved and granted to the reporting person. Of the restricted stock units that were awarded, 34,302 will vest immediately and 34,302 will vest quarterly in the next two years.
(3) On December 31, 2015, the reporting person was granted a target of 75,678 shares of restricted stock units in four tranches subject to satisfaction of share price targets over the next four years. The vesting of restricted stock units in the second, third and fourth tranches is also subject to the satisfaction of certain operational goals, as determined by the Compensation Committee of the Company. All restricted stock units are subject to time based vesting. Once vested, one-third of shares have no sales restrictions and are sellable on January 1, 2020, one-third of the shares have sales restrictions until January 1, 2021 and one-third of the shares have sales restrictions until January 1, 2022.On February 7, 2017, the Compensation Committee of the Company determined that one of the five share price targets for the first tranche of restricted stock units had been satisfied, which resulted in 4,876 shares being granted, subject to time based vesting described above.

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